Dual chambered, active vibration damper with reactive force producing pistons

ABSTRACT

An actively controlled mount system to control vibration which permits static forces from a machine while decoupling transmission of dynamic vibration forces. The mount system includes opposed force chamber (156, 160) with pistons which control movement of an engine connected bushing (3) to allow compensatory force generated by the opposed chambers to transfer thereto to attenuate vibration from the engine.

This is a division of application Ser. No. 07/506,202 filed Apr. 9,1990.

FIELD OF THE INVENTION

The present invention relates generally to the field of machine andengine mounts, and more particularly, to an actively-controlledvibration reducing mount.

BACKGROUND OF THE INVENTION

Many machines such as engines, motors, compressors and the like, areconnected to suitable supports via intermediate mounts. An hydraulicexample of such a mount may be seen in FIG. 1. Engine 23 is supported bybracket 11 and working bushing 3. The bracket 11 is further connected,via the working bushing 3, to hydraulic mount 5. Hydraulic mount 5 ismounted onto a chassis 9 via a mount bracket 7. Such mounts are intendedto isolate vibration, but must also be capable of supporting the weightof machine, engine, or motor and the like, and damping low-frequencyforces of the machine relative to the support. These motions are causedby normal operations including variations in engine speed, load torquereaction, etc. The design of such mounts is largely dependent upon thenature and types of forces transmitted between the machine and thesupport. In some applications such as gas-powered automobile engines,the mount may simply be an elastomeric block.

In other cases, such as a diesel engine, the mount may take the form ofa spring and damper arranged in parallel with one another. There isunwanted forced transmissability in passive mounts due to the mountresonance and in the case of a parallel spring and damper, the damperinadvertently acts as an unwanted force transmitter at higherfrequencies.

To overcome this problem, it has been proposed to add "active" elementsto such machine mounts. Theoretically, such elements can be selectivelycontrolled so as to effectively cancel the net dynamic forcestransmitted through the spring and damper due to vibratory motion of theengine. It has conventionally been proposed to install anelectromagnetic force motor, or "shaker" in parallel with the spring anddamper of each mount. An accelerometer mounted on the support in thevincity of the mount, supplies a signal to a controller which operatesthe "shaker" to produce an output force of like magnitude but 180degrees out of phase with respect to the sum of the vibration forcestransmitted through the spring and damper, such that the net forcetransmitted through the suspension is substantially reduced to zero.

A further conventional system for actively controlling the vibrationalforces exerted from an engine is disclosed in an article entitled"Open-Loop Versus Closed-Loop Control for Hydraulic Engine Mounts" byGraf et al and published in S.A.E. publication number 880075, publishedin 1988. The hydraulic mount system includes a rubber structure cappedby thin metal plates at both ends. A metal bushing carries the load ofthe engine and is situated between two compliant fluid reservoirs.Motion of the metal bushing is controlled via a close-coupledservo-valve to deliver pressurized hydraulic fluid alternately toopposing reservoirs within the mount. This permits an active mount toimpart either an attractive or repulsive force between the power trainand chassis.

Recently there have been attempts to drive a bidirectional hydraulicmount directly with a controllable pump mechanism. Such an approachavoids the need for a separate bidirectional servo-valve and pump. Suchan approach was described in published PCT application WO89/05930published Jun. 29, 1989. In this approach the pump was physicallyseparated from the mount and hydraulically connected thereto withhydraulic lines.

The above approach has not proved particularly successful as it was notpossible to transmit enough force from the pump to the mount.Additionally, separate mounts and pumps were necessary.

In the system of this PCT application, a spring and damper are arrangedin parallel with one another between the masses. The damper has firstand second fluid-containing chambers, continuously communicating withone another through a restricted orifice. The PCT application attemptsto use the pump to create a net pressure differential across the orificeto reduce the dynamic force attributable to such relative motion betweenthe masses and transmitted through the spring-and-damper. The pump isarranged such that an attempt is made to substantially cancel thedynamic force transmitted through both of the spring-and-damperattributable to such relative motion between the masses.

However, though the conventional systems previously mentionedidealistically appear to provide systems in which a fluid displacementgenerating device produces a desired pressure drop across an orifice ofsuch polarity, magnitude and phase, so as to oppose and reduce certainforces transmitted through a spring and damper combination, they do not,in actuality, operate in such a manner. Power inefficiencies occur dueto pumping the hydraulic fluid, and further losses exist in producingproper forces to actively control and account for machine vibration.Further, by utilizing a fluid displacement generating device, or similartype electrohydraulic servovalve, a bulky package is produced which isdifficult to implement to provide a practical actively-controlledmachine mount. Still further, inefficiencies result due to "bulging"along nonworking mount axes. "Bulging" is an action which exists suchthat the walls in particular chambers do not allow for accurate forcetransmission via the liquid flowing through the particular chamber.

The following analysis indicates the issue regarding pumping fluid inthis application. The following description and analysis of fluidpumping will be illustrated with regard to FIG. 2(a) and 2(b). FIG. 2(a)illustrates a conventional system, showing a particular length of tubingthrough which fluid must flow. A piston attached to a drive motor canprovide a force (F1 as shown in FIG. 2(b)) to push a column of fluid ata particular frequency. The column of fluid has a mass M₁ as shown inFIG. 2b). The force, F₂ as shown in FIG. 2(b) is the remaining forceavailable to displace a working "bushing" of an active mount. Thisbushing, for example, can be seen with regard to 3 of FIG. 1. FIG. 3 isa representative curve of the characteristics of a whole series of plots(not shown) showing the effect of the frequency function on causingincreasing loss of available force. Clearly, the effect of this loss isnot as important at "low" frequencies as it is as "high" frequencies.

OBJECTS AND SUMMARY OF THE INVENTION

In order to alleviate the effect of wiring loss of force at increasingfrequencies, the mass of the fluid being pumped or the length (for agiven tube diameter) of fluid travel should be reduced. The resistanceof the fluid transmission path should also be reduced.

It is therefor an object of the present invention to alleviate theeffect of the loss of force at high frequencies by minimizing both themass of fluid being pumped and the mass and velocity of fluid travel.

In order to minimize the mass of the fluid being pumped, the shortestpossible passageway length for a given cross-sectional area should beutilized as well as the smallest volume in both the mount chambers andthe cylinder/piston chambers.

Therefore, it is a further object of the present invention to utilizepassageways as large in diameter as possible in order to minimize thevelocity of pumping fluid.

It is therefore a further object of the present invention to utilizepassageways which are both short and of large cross sectional area toreduce any loss of force exerted by the fluid pump.

It is a further object of the present invention to collocate the mountand driver in the same housing to achieve an optimal solution. Thisallows the lengths of passageways to be as short as possible. Also, thepassageways can be large in diameter and not unduly contribute to theoverall package size as they would in a noncollocated arrangment.

It is a further object of the present invention to provide a collocatedhousing including a fluid displacement generating device and furtherincluding short and wide fluid transfer passageways for providing forcesto an engine to permit the forces to be transmitted from a machine to asupport while decoupling the transmission of dynamic vibrational forces.

Still further, it is an object of the present invention to provide, inthis collocated system, first and second fluid chambers surrounded by aresiliant rubber material configured to minimize the affect of "bulging"in nonworking areas and to provide proper force transfer to an enginemount, while providing a rigid steel frame in a second area of thecollocated housing to allow proper force transfer to and from therespective first and second chambers, via an actively controlled fluiddisplacement and generating device.

It is a still further object of the present invention to provide anactively-controlled machine mount which minimizes power loss in themount system due to fluid mass and pumping velocity.

It is a still further object of the present invention to provide anactively-controlled machine mount which allows minimization of powerloss through an optimal use of short, large diameter passageways throughwhich fluid is forceably pressured, in a steel rigid chamber, such thatthe forces from the fluid are exerted on a rubber-like material tocounteract dynamic forces exerted from an engine or other type ofmachine.

It is yet another object of the present invention to prevent "bulging"of an elastomeric element in non-working directions by providing eitherfabric or metal reinforcements in the areas of the assembly concerningthese non-working directions.

The objects of the present invention are fulfilled by an apparatus foractively controlling and compensating for static and dynamic forcesexerted from a vibrating element. The apparatus includes a fluid filledforce producing chamber, including a force producing means, forgenerating force through flow of the fluid in response to detection ofrelative static and dynamic forces exerted by the vibrating elements.The apparatus further includes first and second fluid filled forceexertion chambers, each connected to the force producing chamber througha first and second short, wide passageway, respectively, each of thefirst and second fluid-filled force exertion chambers receiving a forceequal in magnitude but opposite in phase by the other of the forceexertion chambers, and exerting the received force to thereby compensatefor the static and dynamic forces exerted by the vibrating element.Preferably, the force exertion chambers, force producing chamber andpassageways are housed within a single self-contained enclosure.

These and further objects of the invention will become more readilyapparent from the understanding of the preferred embodiments withreference to the following drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only and are not intended tolimit the present invention, and wherein:

FIG. 1 schematically illustrates a basic engine mount;

FIG. 2(a) illustrates conventional actively-controlled machine mount;

FIG. 2(b) is a free body diagram of the length of a fluid tube utilizedwithin a actively-controlled hydraulic machine mount;

FIG. 3 is a graphical representation illustrating the increasing loss ofavailable force as a function of frequency;

FIG. 4 illustrates a single self-contained actively-controlled machinemount of a first preferred embodiment of the present invention;

FIG. 5 illustrates an integrally combined actively-controlled machinemount of the second preferred embodiment of the present invention; and

FIG. 6(a) illustrates sectional side views of a third embodiment of thepresent invention;

FIGS. 6(b) and 6(c) are top and side views, respectively, of the thirdembodiment of FIG. 6(a).

The above-mentioned drawings will be described in detail in thefollowing description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 4 illustrates the first embodiment of the present invention, namelya single, self-contained actively-controlled vibrating element mountwhich permits static force to be transmitted from the vibrating element,i.e., a machine, motor, or engine, for example, to a support through aspring-and-damper type arrangement while decoupling the transmission ofdynamic vibrational forces. This particular embodiment of the presentinvention allows minimization of power loss in the mount system due tofluid mass and pumping velocity. The single, self-containedactively-controlled vibrating element mount of FIG. 4 is illustrated byelement 142. The outer casing of the device, or "clam shell", allows theentire mount to be housed within a single unit. This singleself-contained unit is of a three-dimensional generally rectangularshape, and contains an outer wall, 124, which may perferably be made ofsteel, but could be made with a rubber-like material. This outer wallserves to absorb any residual force exerted by an engine, or othersimilar type vibrating element.

The engine, or vibrating element 23, is attached to bracket 11. Thebracket 11 may be one, for example, which is attached to each of thefour corners of the engine to thus support the engine. One particularbracket 11 connected to one particularly actively-controlled vibratingelement mount, will be described with regard to the present invention.It should remain clear, however, that the present invention is notlimited to one such actively controlled vibrating element mountconnected to one engine bracket. This is merely for illustrativepurposes. It should be known that a number of actively-controlledvibrating element mounts may be supplied, one for each of the enginebrackets, respectively. In a rear-wheel chassis design studied by thepresent inventors, there was potential for placement of threeactively-controlled vibrating element mounts. It should be noted,however, that experimental evidence suggested that front mounts were farmore critical to the frame vibration reduction than the rear enginemount. Roughly eighty percent of the engine weight is supported on thefront engine mounts. For this reasons, as well as practicalconsiderations, such as cost and complexity, in a further preferredembodiment, independent actively-controlled vibrating elements mountsneed be utilized at the front two mount locations only.

The engine bracket 11 is one, in a preferred embodiment, of a wishboneshape. The top of the wishbone shape is connected to the engine. The twobottom parts of the wishbone shape in this preferred embodiment are eachconnected to a bushing 3 on alternating sides of the self-containedactively-controlled vibrating element mount of FIG. 4, at a location ofsubstantially the midpoint of the height dimension of the self-containedmount as shown by 3 in FIG. 4, for example. Bushing 3 is located betweenthe first and second symmetrical chambers, 130 and 132, of theself-contained mount, such that force can be equally applied to thebushing from the top or bottom of the bushing in a uniaxial manner, tothereby adequately support the vibrating element as well as decouple thetransmission of dynamic vibrational forces. While chambers 130, 132 aresymmetrical in the preferred embodiment, they need not be so. Stillfurther, the self-contained mounts 24a, 24b are further bracketed to theframe as at 125b or chassis 9 of the device housing the vibratingelement. Further, the bushing 3 is connected via an axle (not shown) toa second bushing on the opposite side of the mount. The second bushing,similar to the first bushing 3, is then connected to the second wishboneleg of the engine bracket 11. Therefore, the bushing 3 more adequatelyreceives the force from the engine, including both the static forcetransmitted due to the weight of the engine, as well as the dynamicvibrational forces attributable to motion of the engine and controlledby the active vibration control system.

The self-contained mount is substantially rectangular in shape in the Xand Y dimensions illustrated and further extends in the Z direction (notshown) a distance substantially equivalent to that illustratedcorresponding to the X direction. The clam shell or outer periphery 124of the mount is formed of steel which may be coated with a rubber-likematerial and which is of sufficient stiffness to maintain constantrigidity of the clam shell while still allowing adequate distribution ofthe forces through the mount to compensate for the dynamic vibrationalforces of the vibrating element, as well as absorbing static forcestransmitted from the vibrating element.

FIG. 4 further illustrates that the self-contained device includes thecubic outer housing and a single fluid containing inner cavity includingsubstantially three primary chambers. The main chambers within the mountare illustrated by a first uniaxial force exertion chamber 130 and asecond uniaxial force exertion chamber 132. The chambers 130 and 132 arefluid-filled and substantially equivalent in shape and volume. The fluidis a substantially incompressable liquid. The chambers 130 and 132 aredesigned to be inverted in shape such that the first and second forceexerting chambers form inverted frusto-conical force exerting chambersconverging on the axis of bushing 3. Thus, these juxtaposed chambers ofinverted frusto-conical shape can apply force to the bushing 3 in auniaxial manner. While in the preferred embodiment these chambers arefrusto-conical, any chamber shape may be utilized with optimization ofuniaxial force transmission being a primary objective. For example, thechambers 130, 132 may be frusto-pyramidal or cylindrical in thealternative.

First and second fluid passageways 144, 146 exist in the inner cavity.Force is actively transferred to the first and second force exertingchambers respectively, via these passageways to compensate for thevibrational forces of the vibrating element. These passageways are, inthe preferred embodiment, cylindrical, of large diameter and shortlength. Finally, a fluid-filled cylinder 152 is contained in the cavitythrough which compensational forces are generated via a short-strokepiston 122 and a motor 120. Motor 120 may be any compatible motor suchas a force or displacement electric motor or other actuator convertingcontrol signals into hydraulic forces. This fluid-filled forcegenerating chamber is preferably of a cylindrical shape, as arepassageways 144 and 146. However, the chambers and passageways are notlimited to cylinders and may be modified to suit the needs of one ofordinary skill in the art. The force generating chamber 152 alsoincludes a steel sleeve 128 around the periphery of the cylinder, toensure rigidity of the pumping chamber and good sealing properties suchthat use of the short-stroke piston 122 operates properly andefficiently. The steel sleeve 128 extends around the periphery of thecylinder 152, but does not cover passageways 144 and 146. The openingsof the passageways are wide circular openings 148 and 150, and serve toallow force transfer to chambers 130 and 132, and thus are not steelcovered and therefore remain open. The self contained cavity isseparated into the various chambers and passageways by an inner rubbermaterial 140. The rubber material may be hollow rubber or solid rubber.

The force motor or any similar type actuating device, is actuated so asto operate the piston at harmonic intervals corresponding to thevibration of the vibrating element. Thus, the pump piston 122 may beselectively operated so as to move the pump piston upwardly ordownwardly as desired. The motor 120 should be capable of selectivelymoving the pump piston relative to its force generating cylinder in thedirection desired and at the desired frequency and amplitude.Preferably, the pump-piston operates within cylinder 152 betweenpassageways 144 and 146 to produce a short stroke within thefluid-filled chamber 152 to generate and transfer force to chambers 130and 132 which are adapted to convert hydraulic force into mechanicalforce through the action of pump piston 122.

The control system utilized to actuate the motor 120 contains anaccelerometer 129 mounted on the frame 9 to sense vertical accelerationof the support, and arranged to supply suitable input signal to acontroller 172. A frequency sensor monitoring motor harmonies (typicallya fly wheel tachometer 125) is mounted to the vibrating element 23 tosense the frequency of the vibration of the vibrating element 23, and tosupply another input signal to controller 172. The controller 172 mayoptionally be arranged to supply a suitable output signal indicative ofthe desired position of pump piston 122 relative to its cylinder 152, asa positive input to a summing point 133. A residual pump piston positionsensor 127 may be arranged to sense the actual position of the pumppiston 122 and to supply an appropriate signal as a negative input tothe summing point 133. These two input signals are sun, ned in summingpoint so as to drive the pump piston 122 to produce a force signal of adesired polarity, magnitude, frequency and phase. However, the pumppiston position sensor may be removed such that the controller 172 canprovide a force output signal independent of pump position. In thepreferred embodiment, however, no such position control is utilized andthe pump piston position sensor 127 and summing point 133 areeliminated. An example of the control system used in the preferredembodiment to drive the motor of the present invention is shown in U.S.Pat. No. 4,878,188, issued to Ziegler, Jr. on Oct. 31, 1989, thedisclosure of which is incorporated herein by reference. However, anycontrol technique which minimizes below mount force transmission may beused according to the teaching of the present invention.

As previously stated, chambers 130 and 132 are force applying chambersof a frusto-conical shape, inverted with respect to one another. Thefrusto-conical shape of the force activating chambers allows the forceapplied by the mount to the engine, to be unidirectional in the Xdirection, as indicated in FIG. 4. Further, the frusto-conical shape ofeach of the force activating chambers 130 and 132 is such that thelargest base of the cone is furthest from the bushing 3, in each of thechambers. Thus, the frusto-cone containing a short and a long base,parallel to one another, are inverted so as to juxtapose the short basesof each of the chambers 130 and 132 closest to bushing 3. Thus, thefrusto-conical shape allows any force exerted to be exerted in aunidirectional manner at the bushing 3, to compensate for vibrationalforces in the engine. A significant feature of this mount design is thatforces are controlled in the uniaxial direction while the vibratingelement is free to move in all other directions.

A cylindrical orifice or bleedhole 134 is also shown connecting chambers130 and 132. The orifice 134 acts as a high pass mechanical filter toprotect the actuator and may control dynamic forces exerted at very lowfrequencies. It further allows the bleeding of air from the systemduring initial construction.

The chambers 130 and 132 may further contain a fabric, metal or othermaterial 131 arranged such that it will further channel force in anaxial (X) direction towards bushing 3 in each of the chambers 130 and132. This stiffner 131 should be compliant in the axial (x) directionand stiff in other directions. This stiffner 31, within the walls of thechambers 130 and 132, combined with the chamber shape, allows forenhanced mount efficiency by reducing "bulging" in non-working axes bychanneling forces in the working or "x" axis.

The force generating cylinder 152, housing the short-stroke pump piston122, contains a steel sleeve 128 along the inner wall in closingsubstantially all of the cylinder 152 except that of openings 148 and150. These areas 148 and 150 lead to passages 144 and 146 through whichforce generated by the pump piston is transferred in synchronizationwith the vibration of the vibrating element via the force motor andpreviously mentioned control system to the force activating chambers 130and 132, to thus apply compensatory force to thereby actively controland compensate for engine vibration. When the engine or similarvibrating element is exerting a force downwardly toward the support, thepump piston may be moved so as to simultaneously track or anticipatethis force, inhibiting the vibration by matching the velocity of thevibrating element.

Passageways 144 and 146 are short in length (1) and wide in diameter (orcross-sectional area)(D) to transfer force generated from the pumppiston in chamber 152 to chambers 130 and 132 as previously described.It is essential to minimize force lost between the initial force (F1)generated by the pump piston, to the final force (F2) generated throughchambers 130 and 132 and applied to the vibrating element 23 throughbushing 3. The chambers 130 and 132 are surrounded by substantiallyrubber-like walls such that the chambers operate as if the spring anddamper were integrally combined in one unit.

Essentially, via the control system, a piston 122 attached to a forcemotor 120 can provide a force (F1) from a column of fluid, at aparticular frequency. The column of fluid contained within the chambersof the mount, has a mass M. The force (F2) is the remaining forceavailable to displace the bushing 3 of the active mount to activelycontrol the vibrations exerted from the vibrating element. It isdesirable to minimize the loss of force, (F1-F2), to maximize force, F2,exerted through the force activating chambers 130 and 132 in theuniaxial (x) direction. To maximize force transferral, the mass of thefluid must be as small as possible and/or the length of fluid travelmust be minimized. The forces are dictated by the following equation:

EQUATION 1

    F1-F2=Ma=-ω.sup.2 Mx=-ω.sup.2 ρAx

Where

M is the mass of the fluid;

a is acceleration;

ω is angular frequency;

x is displacement distance;

ρ is a constant; and

A is cross-sectional area of the fluid.

Further, this leads us to the vibrational force needed to activelycontrol the vibrating of the vibrating element, F2, is equal to F1-ω²ρlx. F1 is the force available from piston 122 as a given frequencywhile F2 is the residual force left after the transmission process.Thus, F2 is dictated by the equation:

EQUATION 2

    F2=F1+ω.sup.2 ρAx.

Therefore, in order to minimize the mass of the fluid being pumped, theshortest possible length of passageways 144 and 146 should be utilizedas well as the smallest volume in the passageways as well as the fluidwhich must be displaced in both the force exerting chambers 130 and 132and the force producing chamber 152. Further, in order to minimize thevelocity of the pumping fluid, the passageways should be as wide indiameter as possible. An optimized solution requires passageways 144 and146, to be both short and wide to reduce the loss term of equations 1and 2. Since the force acting chambers and force producing chamber arecollocated in a single self-contained housing, the length of thepassageways tubes 144 and 146 can be optimized to be as short aspossible. Also, the passageways can be large in diameter (D as shown by148 and 150) so as to not unduly contribute to the overall package sizeas they would in a non-collocated arrangement. Thus, it is desirableaccording to the teachings of the present invention, in this firstpreferred embodiment, that the passageways 144 and 146 of FIG. 4, be asshort as possible, and that D, corresponding to the diameters of thepassageways 144 and 146, be as large as possible. This allows forminimal pumping velocity of the fluid and further facilitates of thesmallest fluid mass at that velocity. Thus, the force F1 generated bythe piston in cylinder 152 can be transferred and be utilized to act ina uniaxial manner (corresponding to the X direction of FIG. 4) on thebushing 3 with minimal force loss so as to thereby cancel vibrationalforces over the frequency range of control, as generated by thevibrating element. Thus, dynamic forces transmitted by the vibratingelement through the suspension bracket 11 and overall suspension systemand attributable to such high frequency vibration, will be at leastreduced and preferably eliminated.

Further, as is shown in FIG. 4, there also exists a orifice or bleedhole 134 which connects the opposing and inverted frusto-conical forceacting chambers 130 and 132, and functions as a dampening orifice forextremely low frequencies. This preferably cylindrical orifice 134connecting chambers 130 and 132 is substantially small in diameter suchthat it operates primarily at very low frequencies and does notinterfere in the force transfer from cylinder 152 to chambers 130 and132 in the actively controlled frequencies of interest.

The inner rubber 140 segmenting the clam shell into the previouslymentioned three chambers, can be made of solid or hollow rubber materialas previously described. The material must be sufficiently still enoughto maintain rigidity but also flexibile enough, when used with bleedhole134 to be compliant in the uniaxial direction. The inner rubber material140 which allows for the division of the single self-contained cavityinto the previously mentioned three chambers, also provides for theshape of these chambers. As previously mentioned, chambers 130 and 132are opposing inverted frusto-conical shaped to allow the channeling of adynamic compensation forces in a uniaxial direction. The circularopenings 148 and 150 leading from the piston cylindrical chamber 152 aresubstantially circular in shape.

The pump piston 122 is preferably a short stroke piston which operatesin sealing contact with the steel sleeve, as shown by 141, to therebyoperate between cylindrical openings 148 and 150. Thus, depending on theforce exerted by the engine, the piston can provide a compensatory forcefrom cylindrical chamber 152 through the tubular passageways 144 and 146into chambers 130 and 132, thus apply the proper compensatory force tothe engine through bushing 3.

It should be further noted that the design of the device in FIG. 4 andthe location of the cylindrical pump piston chamber and the tubularpassageways 144 and 146 may be varied. For example, as long aspassageways 144 and 146 are essentially the same length and same shape,they may enter chambers 130 and 132 at a variety of angles throughoutthe device. Further, it should be clear from FIG. 4 that the location ofthe pump piston and force motor is merely one of design choice and maybe varied or would vary to one of ordinary skill in the art. Forexample, the axis of the pump may be different from the axis of uniaxialdisplacement (x) of the chambers 130, 132.

Still further, other obvious modifications of the device can further beimplemented such that the configuration also allows for the use of asecond force motor, if needed, to produce additional force and fluiddisplacement, separately to each of chambers 130 and 132.

In a second preferred embodiment of the present invention, anactively-controlled vibrating mount is shown with regard to FIG. 5. InFIG. 5, an actuator 176 is illustrated which provides the appropriatelycontrolled compensatory pumping force from a control system similar tothat previously described with regard to FIG. 4. Such a system, forexample that illustrated in U.S. Pat. No. 4,878,188 issued to Ziegler,Jr. on Oct. 31, 1989, may further be utilized to selectively create adesired compensatory force to anticipate the force exerted by thevibrating engine, the anticipating force being of such magnitude,polarity and phase to substantially eliminate the static and dynamicforces transmitted through bushing 3. Further, the forces exerted arearranged to substantially cancel vibrational forces over the frequencyrange of control. Typically these vibrations are harmonic in nature andare controlled via adaptive techniques. However, once again, any desiredtechnique may be used. Thus, similar to pumping chamber 152, theactuator applies the necessary compensatory force through a firstpassageway 181 and a second passageway 183. A single piston and motorarrangement may be utilized, similar to that of FIG. 4, or a separatepiston and motor arrangement can be utilized for each passageway 181 and183 such that compensatory forces of equal magnitude and opposite phaseare generated through each passageway.

Passageways 181 and 183 are designed to be oval or cylindrical fluidcontaining cavities within a two piece aluminium bracket 184. Thebracket 184 is customized to fit each particular vehicle and is of asubstantially cubic shape, somewhat similar to that of the clam shell ofFIG. 4.

The bracket 184 is substantially cubic in shape, as previously stated,and provides for an aluminum housing around the actively-controlledvibrating element mount. An inner housing lies substantially within thecubic aluminum bracket and includes a rubber mount 180. The rubber mountis shaped substantially as a first and second integrally connectedopposed frusto-conical shaped chambers, with the base of the conesattached to the top and bottom of aluminum bracket 184, and the smaller,in area, tops of the frusto-conical shaped chambers converging on theactual bushing 3. Cavities or exertion chambers 156, 160 are arranged inrelationship to bushing 3 so as to convert hydraulic force to mechanicalforce. The rubber mount 180 surrounds bushing 3 the x and y direction asillustrated in FIG. 5. Thus, as a force from a vibrating element istransmitted through bushing 3, compensatory forces can be generated viaactuator 126 and travel through oval passageways 181 and 183 which maybe of any desired cross-section but which are oval in the preferredembodiment such that they provide the proper compensatory force throughbushing 3 and thus control the vibrations of the vibrating element.

The oval passageways 181 and 183 provide passageways analogous to 144and 146 of FIG. 4 through which the compensity force is generated. Thepassageways are oval in shape, as previously mentioned, such that thelength L in passageways 181 and 183, is substantially minimized to be asshort as possible to minimize the mass of fluid pumped, similar to thatpreviously described with regard to FIG. 4. Further, in order tominimize the velocity of the pumping fluid, the passageways areconfigured to be as wide in diameter as possible, as shown at entranceportions 194 and 196, prior to the fluid entering force activatingchambers 190 and 192, the chambers being analogous to chambers 130 and132 of FIG. 4. Still further, an orifice 188 exists in a uniaxialdirection connecting force activating chambers 190 and 192 to act in asimilar manner as orifice 134 of FIG. 4.

Further, o-ring seals 182 exist to ensure no pressure is lost betweenchambers 190 and 192 and oval passageways 181 and 183, as well as o-ringseals 174 ensuring a fluid tight connection between the actuator 176 andthe actual bracket.

FIG. 5 further shows that the outer chamber 184 containing passageways181 and 183 is integrally combined in one unit with rubber mount 180.Thus the chambers 190 and 192 can receive compensatory force via thefluid filled passageways 181 and 183 in a short, compact device, fromactuator 176. Thus, loss of force is minimized.

As can be seen by FIG. 5, the actuator provides the proper compensatoryforce through either of the transmission passageways 181 and 183, thelength of the fluid filled passageways, i.e. the force loss, isminimized and the velocity of pumping fluid is further minimized by thelarge diameter openings 194 and 196. This occurs in a similar manner aspreviously described regarding FIG. 4. Thus, by housing the forcetraveling passageways 181 and 183 within the bracket 184, integral withrubber mount 180, space and area within a vehicle, for example, may alsobe conserved.

It should be clear to one of ordinary skill in the art that actuator 176may comprise a dual chamber pump and drive motor as exists in FIG. 4, ormay contain multiple force motors and piston devices, one for each ofthe oval passages 181 and 183 to apply the appropriate force, equal inmagnitude and opposite in phase, through each of the passageways.Similarly, it should be noted that one of ordinary skill in the artcould construct the force exerting chambers 190 and 192 in an optimalshape so as to maximize and isolate the force exerted on bushing 3 in auniaxial direction, similar to that of the first embodiment of FIG. 4.Still further, as in the case of FIG. 4, it should be noted that mount180 is of a rubber material so as to be resiliant enough to allowflexibility in the desired direction to transfer force, but furtherrigid in other directions so as to avoid any problems such as "bulging"of the mount and non-working directions. Force, similar to thatdescribed in the previous embodiment, is exerted on the bushing 3 in auniaxial direction. It is further noted that the rubber mount may bemade of any elastomeric element. It should also be noted that uponutilization of a first and second force motor and pump piston assembly,to supply force through passageways 181 and 183, that the propercompensatory force would be generated by asserting a positive half ofthe proper force through first one of passageways 181 and 183 andasserting an essentially equal in magnitude force, opposite in phase,through the other passageways 181 and 183. Thus, the two chambers, 190and 192, operating in synchronism via the actuator 176, would providethe proper compensatory force for stabilization of the vibrating elementthrough bushing 3. Chamber 190 and 192 are arranged in relationship withbushing 3 so as to convert hydraulic force to mechanical force.Similarly, if one of ordinary skill in the art wereto utilize twoshort-stroke pump piston assemblies in the first embodiment in thepresent invention as shown in FIG. 4, a similar positive and negativeforce would be applied through passageways 144 and 146 to provide theproper compensatory force and the uniaxial direction for the vibratingelement through bushing 3. Operation of the system of the secondembodiment occurs similar to that of the first embodiment and thus sucha description is not included.

A third preferred embodiment of the present invention is shown withrespect to FIGS. 6(a), 6(b) and 6(c) illustrating various views of thethree dimensional two cavity, self-contained actively-controlledvibrating element mount. The mount in this embodiment is substantiallycylindrical in shape (but may be of any desired cross-section) andcomprises a single self-contained unit having first and second cavities.This mount is constructed of a steel body 154 having first and secondcylindrical chambers 156, 160, including rubber elements, 158, which areattached to the metal bushing 3 through a coupling rod 157. The bushing3 is connected to a support 11 for a vibrating element 23 via an innermetal rod, 168. This inner metal rod 168 and bushing 3 intersect rod 157to thus allow compensatory force generated from the first and secondchambers to transfer to the bushing 3 to thus control transfer ofvibration from the vibrating element 23.

Within the first and second steel body cylindrical chamber 156, 160,exist a first and second drive motors 151 and 166 which may be suitableforce or displacement motors, and first and second short-stroke pumppistons, 153 and 162. Fluid is present in each of the cylindricalchambers 156 and 160 such that force created through the motor andpiston combination can be transmitted to the bushing 3 in a similarmanner as previously described with regard to FIG. 4, such that acompensatory force can be applied to metal bushing 3 and thus controlvibrating element 23. Further, an elastomeric material 158 is providedat the ends of each chamber 156, 160, opposite to that of the motors.This elastomeric material 158 aids in uniaxial force transfer of theforce generated in each cavity to adequately compensate for thevibratory force of the vibrating element through metal bushing 3. Theelastomeric material 158 and the steel body constrain fluid expansion inthe non-working axes and provide force transfer only in the workingaxis, through coupling rod 157. Further, similar to that of FIG. 4, anorifice 165 is provided.

The use of two force motors in this type of package assembly for themount requires only electrically external connections to a controller172. Inverter 170 schematically represents the phase inversion appliedto one of said motors 151, 166 and exists such that the compensatoryforces can be applied equal in magnitude and opposite in phase, bymotors 151 and 166 such that the two chambers 156 and 160 allow thetransfer of force in a push-pull type of motion. Thus, the propercompensatory force can be achieved through metal bushing 3.

As can clearly be seen in the operation of the self-contained, twocavity actively-controlled vibrating element mount shown in FIGS. 6(a),6(b) and 6(c), a less bulky package is provided which sufficientlyreduces the amount of inefficiencies due to "bulging" in non-workingaxis.

It should further be noted that in FIGS. 6(a), 6(b) and 6(c), the lengthof the force activating cylindrical chambers 156 and 160 is clearlyminimized. Thus, the mass of the fluid being pumped is minimized throughthe shortest possible tube length to thereby achieve optimum results aspreviously described regarding FIG. 4. Further, in this embodiment ofthe present invention, the need for passageways 144 and 146 of FIG. 4,for example, is essentially eliminated due to the direct application ofthe force from the motor and piston combination 151 and 153, forexample, to the metal bushing 3. There is no intermediate length of apassageway through which the fluid must pass which may allow for loss offorce, as previously illustrated with regard to Equation 1. Stillfurther, cylindrical chambers 156 and 160 are short in length and alsoextremely wide in diameter. Thus, the velocity of the pumping fluid isfurther minimized for reasons similarly given regarding FIG. 4. Thus,the configuration of the present invention as illustrated in FIGS. 6(a)to 6(c) illustrates a self-contained two cavity or two chamber mountwhich allows minimization of power loss through optimal use of short,large diameter cavities or chambers. This configuration realizes theutilization of two force motors and their application.

From the above-described embodiments of the present invention, it isapparent that the present invention may be modified as would occur toone of ordinary skill in the art without departing from the spirit andscope of the present invention which should be defined solely by theappendant claims. Changes and modifications of the system contemplatedby the present preferred embodiments will be apparent to one of ordinaryskill in the art.

What is claimed is:
 1. A hydraulic system for use in a system foractively-controlling and compensating for dynamic forces exerted from avibrating element, comprising:a mounting bushing supporting thevibrating element, a substantially cylindrical outer housing, first andsecond fluid filled compensatory force generating chambers, provided insaid housing in opposed connection with said mounting bushingtherebetween, said first and second fluid filled compensatory forcegenerating chambers each including a force producing means forgenerating first and second opposed forces in an uniaxial direction,respectively, through flow of the fluid to opposing sides of saidopposed connection, said first and second forces being equal inmagnitude but opposite in phase and being generated in responsetodetection of relative static and dynamic forces exerted by thevibrating element, said first and second forces being uniaxially exertedto thereby compensate for the static and dynamic forces exerted by thevibrating element.
 2. The system of claim 1, wherein the first andsecond compensatory force generating chambers are exteriorly enclosed bya steel body of said substantially cylindrical housing.
 3. The system ofclaim 1, wherein said force producing means in each of said first andsecond force generating chambers includes a motor and a piston forgenerating said first and second opposed forces, respectively.
 4. Thesystem of claim 1, wherein said bushing being centrally located betweenand operatively connected to, said first and second fluid filled forcegenerating chambers.
 5. The system of claim 1, wherein said first andsecond fluid filled force generating chambers further include, a rubbermaterial for channeling said first and second force generateduniaxially, respectively, to aid in the compensation of said dynamicforces exerted by the vibrating element.
 6. The system of claim 1,wherein the amount of fluid flow within said first and second fluidfilled force generating chambers is substantially minimized so as tominimize the mass of fluid flowing necessary to generate the axiallyexerted first and second compensatory forces.
 7. The system of claim 1,wherein the first and second fluid filled force generating chambers areconnected via a small cylindrical passageway to enable compensation forthe dynamic forces exerted at very low frequencies by the vibratingelement.